Look at the photos of Conyza canadensis on FloraSBS Myriam, a full shot shows all narrow leaves. It might depend on growing conditions, or a quirk of the species.
https://sites.google.com/site/...
Another ..
http://wnmu.edu/academic/nspag...
Maybe it grows larger leaves in healthy soil.
There are other species of Conyza .. the flower bracts seem to be shorter on your plant.
Numerous capitula of Conyza canadensis with very visible white ligules (when compared to the other species of Conyza )
http://invasoras.pt/en/gallery...
https://www.google.co.uk/searc...
https://www.google.co.uk/searc...
https://www.google.co.uk/searc...
The flowers look more like Conyza bonariensis, the leaves I'm not sure about as they seem to vary.
http://www7a.biglobe.ne.jp/~fl...
Another, there's too many to choose from! Best to see which species are growing in the area.
https://www.google.co.uk/searc...
http://www.calflora.net/losang...
Erigeron bonariensis?
https://en.wikipedia.org/wiki/...
Conyza bonariensis is a synonym of Erigeron bonariensis ..
http://www.theplantlist.org/tp...
When I search for "Erigeron bonariensis rio de janeiro" I only get Conyza canadensis ..
https://www.google.co.uk/searc...
